Hybrid integration of III-V semiconductor components with passive waveguides is of increasing importance as a method of increasing the functionality of integrated optical and photonic systems. Applications include: optical communication systems, optical sensing applications, and optical data processing.
A fundamental problem in hybrid integration is that the semiconductor element has a higher refractive index than the passive waveguide. In the case of a III-V semiconductor component integrated on a planar Silica (SiO2) platform, the refractive indices are typically around 3.6 for the semiconductor and 1.5 for the Silica. This refractive index difference causes a number of problems, e.g. there is a high reflection coefficient at the interface between the two devices, and the mode size in each device is different. Both of these effects result in a loss in optical power, reduced coupling efficiency between the two devices, and scattering of light, and undesirable reflections.
It is an object of the present invention to obviate or at least mitigate one or more of the aforementioned problems in the prior art.
Further objects of various embodiments of the present invention include:
enablement of hybrid integration to be carried out, while ensuring good mode matching between active and passive sections;
ease of manufacture;
low loss coupling between active and passive sections.